In an electronic camera and a video camera, focus adjustment is performed by using a contrast detection method in which a proper focus position is detected by analyzing an image signal, which is obtained by an image sensor for taking a subject, and a sharp image is discriminated on the basis of image contrast. As to the contrast detection method, since it is possible to use the image sensor as a detection element, cost is prevented from increasing. Further, since the sharpness of the image is discriminated, focus adjustment is accurately performed. On the other hand, it is necessary in the contrast detection method to analyze the image signal whenever a focus lens moves. Thus, there is a disadvantage in that it takes a time for detecting the focus position. In this regard, there is a known imaging device in which a required time for the focus adjustment is adapted to be shortened by narrowing a moving range of the focus lens in advance (see Japanese Patent Laid-Open Publication No. 2006-18246). In this imaging device, a human face of a subject is detected and a subject distance is estimated from a size of the human face. On the basis of the estimated subject distance, the moving range of the focus lens is narrowed in advance.
However, in the imaging device described in the above-noted Publication No. 2006-18246, the range for performing the focus adjustment of the contrast detection method is merely reduced in comparison with a conventional range. Thus, there is a disadvantage in that the required time for the focus adjustment is not sufficiently shortened. Moreover, a depth of field is calculated, and the focus adjustment is not performed when a main subject is located inside the depth of field. Although the time is shortened by doing so, the focus adjustment of the contrast detection method is performed when the main subject is located outside the depth of field. Consequently, there is a disadvantage in that the time can be shortened in only the specific case.